Last week, New Orleans hosted the annual convention known as Netroots Nation, which started as a fringe gathering of the digital left in 2006 and has become a staple of mainstream Democratic politics.

The celebrity senators Cory Booker and Kamala Harris were there this year to rev up the crowd. So was their colleague Elizabeth Warren, who sent the house into a full-throated roar. Tim Ryan, the Ohio congressman who’s been critical of his party’s older, more coastal leadership, offered up a partisan speech and was rewarded with a rousing response, too.

One 2020 hopeful who wasn’t there was Bernie Sanders. Apparently the party’s Socialist Animal had a scheduling conflict. More likely, though, Sanders simply doesn’t feel the need to compete for activist affection anymore.

The antiestablishment, anti-capitalist movement he ignited two years ago is now a raging wildfire among the party’s base, and Sanders spends a lot of his time showing up for grateful candidates in local races. He and his supporters — along with some of my colleagues in the media — assume that Sanders will enter the presidential field this time as a clear favorite.

He won’t end up that way.

Because next time out, Sanders won’t have an entire stage to himself, with all that space to bask in the adoration of frustrated activists. This will feel more like being packed into the greenroom of the senior-home talent show, with some guy practicing accordion scales on the sofa next to you.

And right now, at a time when Democrats are frantically searching for the anti-Trump, Bernie is starting to look strangely like a reverse image of the president, instead.

Let’s go back for a moment to the Democratic Party of the 1980s, which, as regular readers know, is a period I chronicled in my last book. After shocking the party’s establishment and very nearly wresting the nomination from Walter Mondale in 1984, Gary Hart was the Sanders of his moment. Everyone assumed he’d be the nominee next time around.

As a former campaign strategist himself, however, Hart understood that he would be endlessly bedeviled by what his team dismissively called “the new Garys” — a lineup of first-time Democratic hopefuls who fashioned themselves after Hart and appropriated his language and his ideological appeal.

Hart’s solution was to differentiate himself from the fresher-faced pack with a thick sheaf of substantive ideas and a less conventional campaign style — a strategy that would probably have worked had his second bid, along with his entire political career, not completely blown up in the first presidential sex scandal of the broadcast age.

Thirty years later, Sanders is about to find out what it’s like to be the Man rather than the insurgent, surrounded by cheap Bernie knockoffs. What that means is that he’ll be the guy whose authenticity and viability as a candidate will be under attack.

And how exactly will Warren or Booker or any of the other 25 progressive candidates come at Sanders? Let’s put it this way: I’m nobody’s idea of a brilliant campaign strategist, and I don’t have to think very hard to figure that out.

Start with the sensational trial playing out in Alexandria, Va., this week, where the president’s former campaign manager, Paul Manafort, is charged with engaging in the worst kind of political corruption while working on behalf of foreign autocrats.

The first witness the prosecution called was Tad Devine, Bernie’s chief adviser from the 2016 campaign, who, it turns out, had been working closely with Manafort and charging exorbitant rates for influencing Ukrainian elections. That’s not great.

What has Sanders, that thundering champion of reform and enemy of backroom politics, had to say about any of this sleazy business? Not a word, near as I can tell.

This, by the way, follows revelations that the same Russians who tried to get Trump elected had first tried to help Sanders defeat Hillary Clinton in the 2016 primaries. (Maybe they just remembered Sanders warmly from the time he spent honeymooning in the Soviet Union.)

So is Sanders really the guy to stand up and make the case against foreign influence on our elections, not to mention the fecklessness and greed of the political class?

Let’s not stop there — because I can assure you his opponents won’t. They’ll remind Democratic primary voters that Sanders also refused to release his tax returns during the last campaign, and still does. Sound like anyone else?

They’ll remind you all, as Clinton did in 2016 (although it probably has more resonance now, after Parkland and other shootings), that Sanders voted with the gun lobby against the Brady Bill and for legal immunity for gunmakers — the two most consequential pieces of gun legislation in the past three decades.

They’ll take the opportunity to point out that Sanders, like Trump, is linked to a higher-education scandal — in his case, an investigation into his wife’s tenure as president of a Vermont college that went bust and closed.

And if I were running against Bernie, and we were going to talk about Republican efforts to rig the electoral system, I might also note that Sanders, who identifies as an independent, routinely games the system in Vermont, by filing for the Senate as a Democrat and then declining the nomination, so he doesn’t have to face an actual Democrat on the ballot. He’s doing it right now, in fact.

Also, Bernie will turn 79 in 2020. Trump will be 74. There goes your generational pitch.

So if I’m Warren or Kirsten Gillibrand or Deval Patrick or, I don’t know, Howard Schultz, the thing I say is this: “Bernie, you’ve been great for the party, and we appreciate it. But we need a candidate who can stand on that debate stage and present the clearest, cleanest contrast with Donald Trump. And in too many ways, ideology aside, that just isn’t you.”

You see, the core problem for Sanders is that he’s tried to have it both ways; he’s wanted to hold himself out as above the tawdriness of pragmatism and party politics, while simultaneously making the same calculations as every other ambitious politician. And that was fine, as long as his opponent was the personification of the system he indicted.

But that won’t happen this time. Now the very same case he made against Clinton will be made against him, instead — that he’s too compromised and too controversial, too much like the adversary he’d debate, to take full advantage of the party’s moment.

You know what they say about karma. As Barbara Bush said of another Democratic candidate: It rhymes with rich.